Generally, a paper pipe, a steel sheet or a steel pipe has been used as such a conventional flexible form member. That is to say, in a conventional construction method, as shown in FIG. 18, a paper tube c is arranged at a desired position in a condition of being interposed between an outer form a and an inner form b, then concrete is poured into a space between the above-mentioned outer form a and inner form b in order to form slabs, beams, or walls. The outer form a and the inner form b are removed when the concrete has cured, then the above-mentioned paper tube c is removed thereby to form a through hole.
However, a plurality of reinforcements have been arranged over and under the through holes to be formed, as shown in FIG. 18. In order to arrange a paper tube c whose diameter is larger than a pitch between reinforcements d, the paper tube c should be temporarily deformed into flat and inserted into the space between reinforcements d, then it should be arranged to bridge the outer form a and the inner form b while restoring the original shape. Therefore, it takes much labor and time to make an arrangement for forming a plurality of through holes. In addition, the paper tube c may accidentally be set before it has been restored to the original shape, which will cause a problem that the opening of the through hole deforms.
In order to solve the above-mentioned problem, a method can be conceived that the paper tube c is set after only the reinforcement e under the paper tube c has been arranged, then the reinforcement d over the paper tube c is arranged. However, it deteriorates the work efficiency because it prevents work which involves welding or the like from being continuously accomplished. In addition, the paper tube c which has once been set may be pushed by unexpected force which may arise when the reinforcement d over the paper tube c is arranged thereby to change the position where it should be. Thus it prevents from forming a hole which penetrates the concrete at the predetermined position.
It is an object of the present invention to provide a flexible flexible form member which solves the above-mentioned problems.